A variety of analog to digital converter circuits are known. Analog to digital converter circuits (“ND circuit” or “ADC”) are used to convert analog signals to digital signals. In other words, analog electrical signals that vary continuously are converted by analog to digital converter circuits into digital signals. Digital signals, in contrast to analog signals that vary continuously, vary by stepping from one level to another. Analog to digital converter circuits are applied in a variety of applications, for example, when trying to convert an analog signal into a signal that a digital processor can read and understand. In one example, power supplies can be made to provide power to other electronics in a variety of forms. In one such form, power supplies provide power in the form of direct current (“DC”) power. In such a power supply, a power output is generally constant at a particular voltage, for example, 5 volts.
Many such power supplies include feedback loops to help determine whether the output provided by the power supply is the expected output. A typical feedback system includes a sensor to sense the output of the power supply and a circuit to determine whether the output is within a given range as expected to be provided by the power supply. For power supplies with digital controllers, the signals indicating variance from the expected power output need to be changed from analog signals to digital signals such that the digital controllers can understand and react to correct the output of the digital power supply. Various types of analog to digital circuits for doing this conversion from an analog error signal to a digital signal readable by a digital controller are known and have been applied in such power supplies.
One such analog to digital conversion circuit is known as a flash analog to digital converter circuit or “flash ADC”. Flash ADCs are generally characterized by having a very fast response time and being relatively simple to construct. Flash ADCs, however, lack sufficient resolution for high quality or highly precise power supplies. For example, in order to obtain a resolution suitable for certain precision power supplies, a flash ADC would have to include hundreds of comparator circuit elements. Such circuit sizes are undesirable because the circuit consumes too much power and space.
Another example analog to digital converter circuit used with a digital controller includes high resolution analog to digital converter circuits such as a delta sigma ADC circuit. Such circuits provide much improved resolution over flash ADC circuits. High resolution circuits, however, operate much too slowly to provide the necessary near-instant feedback necessary for maintaining a constant output power from a digitally controlled power supply.